The development and mature function of the mammalian brain must require the precise regulation and concerted action of thousands genes whose products are restricted to the nervous system. The purpose of this grant is to further develop and utilize bacterial artificial chromosomes (BACs) as tools for the discovery and analysis of genes predominantly expressed in the mammalian CNS. The proposal is organized into three specific aims: 1) To utilize BAC transgenic analysis for the characterization of CNS specific gene expression patterns and for the localization of their encoded protein products [BACexpress]. 2) To utilize CNS specific BAC/EGFP or beta-lactamase expressing mice and fluorescence activated cell sorting (FACS) to prepare cell specific probes for gene expression analysis. To use these probes to interrogate either DNA chips or microarrays to profile gene expression for specific CNS cell types (BAC array). 3) To develop and utilize gene trapping in BAC clones to accelerate discovery of CNS specific genes [BACtrap]. The further development of these techniques and their adoption for high throughput analysis can yield: accurate temporal and cell type specific expression profiles for nearly all CNS specific genes; the size, abundance and subcellular distribution of proteins encoded by each of these genes; a library of defined BAC vectors for genetic manipulation of the great variety of CNS cell types; phenotypes resulting from increased dosage of any of the assayed genes; and a "molecular histology" of the CNS that includes the definition of molecularly marked subtypes of morphologically identified neurons.